1. Field of the Invention
The present invention generally relates to wireless local area networks. More particularly, the present invention relates to detecting a hidden node in a wireless local area network.
2. Description of the Related Art
Computers have traditionally communicated with each other through wired local area networks (“LANs”). However, with the increased demand for mobile computers such as laptops, personal digital assistants, and the like, wireless local area networks (“WLANs”) have developed as a way for computers to communicate with each other through transmissions over a wireless medium using radio signals, infrared signals, and the like.
In order to promote interoperability of WLANs with each other and with wired LANs, the IEEE 802.11 standard was developed as an international standard for WLANs. Generally, the IEEE 802.11 standard was designed to present users with the same interface as an IEEE 802 wired LAN, while allowing data to be transported over a wireless medium.
Although WLANs provide users with increased mobility over wired LANs, the quality of communications over a WLAN can vary for reasons that are not present in wired LANs. For example, stations in a WLAN can communicate with other stations in the WLAN through an access point (“AP”). More particularly, each station can have a transmission range within which the station can transmit signals to an AP within the WLAN.
Other stations located within this transmission range can detect signals transmitted by the station. After detecting signals transmitted by the station, these other stations can wait to send their own signals until the wireless medium is free from traffic generated by the station. However, because a station can have a limited transmission range, other stations located outside of this transmission range, typically called “hidden nodes,” can exist in a WLAN. These “hidden nodes” can send signals across the WLAN that can collide with signals sent by the station. This type of collision arising from the presence of “hidden nodes” is typically called the “hidden node problem.”
The collision of messages resulting from the “hidden node problem” can create unacceptable performance and reliability problems in a WLAN. For instance, each message that is interrupted by a collision can be resent according to the IEEE 802.11 standard. However, resending the message can delay the receipt of the message at its destination. In addition, each resent message can consume additional bandwidth in the WLAN. Such delays and bandwidth consumption can affect other messages being sent across the WLAN, thereby creating performance and reliability problems in the WLAN.